Green, Life-Giving and Forever Young

Show somebody a painting of a verdant, botanically explicit forest with three elk grazing in the middle and ask what the picture is about, and the average viewer will answer, “Three elk grazing.” Add a blue jay to the scene and the response becomes, “Three elk grazing under the watchful eye of a blue jay.”
What you’re unlikely to hear is anything akin to, “It’s a classic temperate mix of maple, birch and beech trees, and here’s a spectacular basswood and, whoa, an American elm that shows no sign of fungal infestation and, oh yeah, three elk and a blue jay.”
According to Peter H. Raven, director of the Missouri Botanical Garden, many of us suffer from an insidious condition called “plant blindness.” We barely notice plants, can rarely identify them and find them incomparably inert. Do you think that you will ever see a coma as vegetative as a tree? “Animals are much more vivid to the average person than plants are,” Dr. Raven said, “and some people aren’t even sure that plants are alive.”
But the antidote to plant apathy is at hand. As an unusually cool, sodden April edges toward May and spring’s cheeky blooms can be bridled no longer, botanists urge everyone to venture outside and check out the world through nature’s rose-colored glasses — and the daffodil, cherry blossom, dogwood and lupine ones, too. If this view doesn’t move you, you’re pushing up daisies.
As it happens, plants are not only alive in their own right. They are also the basis of virtually all life on earth, including ours. The core feature of planthood is autotrophy, that is, the happy ability to make one’s own food. Plants essentially eat the sun, transforming solar energy into sugars and starch through the stepwise enzymatic stitchery of photosynthesis. Animals, by contrast, are heterotrophs, defined by their need to devour other organisms — the hard-won fruit and fiber of the suneaters, or the once-removed flesh of herbivores.
Moreover, because plants release oxygen as a byproduct of photosynthesis, plants also give us aerobes leave to breathe. Our atmosphere is currently about 20 percent oxygen, all of it the bounty of the planet’s green-skinned autotrophs. “The most important chemical reaction on earth is photosynthesis,” said Robert DeFeo, chief horticulturist for the National Park Service. “We are all parasites upon it.”
Essential though plants may be to our survival, Dr. Raven emphasizes that they are a radically different form of organism than are animals. Plants and animals have evolved along separate paths for hundreds of millions of years, ever since single cells began pooling their talents into multicelled beings. “Plants have evolved their multicellularity completely separately from animals, and any direct comparisons between the groups are wrong,” Dr. Raven said. “It’s as if plants evolved on Mars, and animals here.”
In addition to their caloric self-sufficiency, plants can be envied for their eternal youthfulness. A plant elongates itself through constant cell growth in two zones of its body, at the very tips of the roots, which grow down into soil or other surface to which the plant clings, and the outer tips of the shoots, from which new leaves, flowers and fruits sprout. Whereas an animal, upon reaching maturity, has almost no young cells left in its body, Dr. Raven said, “in plants the ends of the roots and shoots are always juvenile, always growing, always babies.”
A plant is also always drinking, slurping water and nutrients the only way it can, through its roots. Everything needs water to survive, but another radical difference between the faunal and floral crafts is that while we can drink water and keep it circulating through the body via the bloodstream, water moves through a plant’s body in a continuous stream, entering through the roots, crawling up the stem and evaporating out through little openings, or stomata, in the leaves. In fact, the upward tug of evaporation is what pulls more water up from the soil, as the clingy water droplets follow each other skyward through the hollow capillaries of the plant’s stem and leaves, shinnying as high as 300 or 400 feet above ground in the case of the giant redwoods.
No, there’s no rest for the weary, especially if you’re immobile. Beyond feeding style, perhaps the biggest discrepancy between animals and plants is that animals can move, but plants are of necessity stuck in place. Unable to defend themselves by running away, plants have instead become crackerjack chemists, evolving a vast armamentarium of insect repellents, fungicides, microbicides, ultraviolet blockers and other defensive compounds that human chemists have just begun to tally.
Rootedness also complicates a plant’s love life, which brings us back to the blooming bounty of spring. Plants, like everybody else, want to spread their seed around and diversify their genetic stock through sexual reproduction, but it’s hard to meet fresh faces when you don’t have legs. A number of plant species like pine trees, oaks, cottonwoods and grasses rely on wind to blow their pollen around, with the hope that some of the male sperm contained therein will land on receptive female parts of their far-flung kind. Or if not the same kind, at least something in the same general group: the boundaries between plant species are far more porous than they are in animals, and different species and even genera of plants cross-hybridize with each other surprisingly often.
Nevertheless, wind sex is highly iffy and inefficient, and many species of modern plants, the angiosperms, instead manipulate members of the animal kingdom to serve as yentas in a more discriminating style. The plants offer up brilliant blossoms to entice a specific pollinating insect or bird, which gets drunk on the blossom’s nectar and wants more and so seeks out other blossoms of similar shape, color or scent. And as the bee or hummingbird flits from one favored flower to the next, it incidentally delivers pollen pockets to just the right spots. “We say, isn’t that beautiful, but the precise forms and shapes of flowers are adaptations to attract individual pollinators,” Dr. Raven said. When we eat, we are parasites on the foundational labor of plants; and when we “say it with flowers,” we are plagiarists, too.

Comments (3)

You are brilliant with your thoughts and words! Kudos on a great article.
John G. |

Posted by John | 2007-08-16

Thank you for your compliment, but I don't think that you realize I did not write this article. I am only quoting it. As stated at the beginning of the entry, I read it in the New York Times, and thought others would enjoy it as much as I did.

Posted by Tina | 2007-08-16

You're absolutely right. I realized after I posted the comment that I must have skimmed past the beginning, but regardless it is a great article and thanks for sharing it. John G. |